Method for forming a coating on a hot vitreous substrate by spraying the substrate while heating the zone that is sprayed and product

Abstract

A hot vitreous substrate 1 travels on a conveyor 2 through a coating station 5 where a metal compound is formed in situ on a face of the substrate 1 by pyrolytic decomposition of coating material 9 sprayed towards the substrate from a spray head 6 which repeatedly traverses the substrate path. Radiant heating means 11 located on the side of the substrate 1 being coated directs radiant heat towards the transverse region swept by the zone of impingement 10 of the coating precursor material 9 on the substrate 1.

What we claim is: 
     
       1. A method of forming a metal compound coating on a side of a hot vitreous substrate as it is conveyed along a substrate path through a coating station, comprising the steps of: (a) spraying coating precursor material towards the substrate by means which repeatedly traverses the substrate path, said coating precursor material being deposited on said substrate at a zone of impingement which sweeps transverse regions of the substrate and decomposing pyrolytically to form said coating in situ on said substrate; and (b) directing radiant heat from radiant heating means located on the side of the substrate being coated towards the transverse region swept by the zone of impingement of the coating precursor material on the substrate. 
     
     
       2. A method according to claim 1, wherein step (a) is conducted by spraying said coating precursor material obliquely towards the path of the substrate in a direction leading along the path. 
     
     
       3. A method according to claim 1, wherein said substrate is conveyed in a downstream direction along said substrate path, and wherein step (a) is conducted by spraying said coating precursor material obliquely towards the path of the substrate in a direction leading along the path and in the downstream direction. 
     
     
       4. A method according to claim 1, wherein step (b) is conducted by directing radiant heat from radiant heating means having a black body temperature in the range 900° C. to 1,600° C. inclusive. 
     
     
       5. A method according to claim 1, wherein step (b) is conducted by directing radiant heat from radiant heating means which includes a plurality of heaters disposed along the path of the substrate. 
     
     
       6. A method according to claim 1, further comprising controlling the intensity of radiation directed towards the transverse region swept by the zone of impingement by adjusting the height of the radiant heating means above the substrate path. 
     
     
       7. A method according to claim 1, further comprising controlling the radiant heat so that for any increment of the area of the substrate the temperature of the surface being coated varies, if at all, by less than 15° C. between the time when such incremental area is first coincident with the zone of impingement of the coating precursor material and the time when it is last coincident with that zone. 
     
     
       8. A method according to claim 7, wherein such temperature so varies by less than 10° C. 
     
     
       9. A method according to claim 1, wherein step (b) is conducted by directing radiant heat from radiant heating means which includes a plurality of heaters disposed across the path of the substrate whereby the quantities of heat directed towards different width increments of the substrate are independently adjustable. 
     
     
       10. A method according to claim 9, further comprising controlling the radiant heat so that, for any increment of the length of the substrate, the temperature of the surface to be coated varies, if at all, by less than 15° C. across the substrate width during coating. 
     
     
       11. Vitreous material coated by a method according to claim 1. 
     
     
       12. A method of forming a metal compound coating on a hot vitreous substrate as the substrate moves along a substrate path through a coating station, comprising the steps of: (a) spraying said substrate with a coating precursor material which pyrolytically decomposes to form said coating in situ on said substrate, said coating precursor material being deposited on said substrate at a zone of impingement which sweeps transverse to said path; and   (b) directing radiant heat, from radiant heating means mounted at said station, toward said zone of impingement as said coating precursor material is being deposited at said zone of impingement.   
     
     
       13. A method according to claim 12, wherein step (a) is conducted by directing the spray obliquely toward said path and in a direction leading along said path. 
     
     
       14. A method according to claim 12, wherein said substrate moves along said path in a downstream direction, and wherein step (a) is conducted by directing the spray obliquely toward said path and in said downstream direction. 
     
     
       15. A method according to claim 12, wherein step (b) is conducted by directing radiant heat from a radiant heating means having a black body temperature ranging from 900° C. to 1,600° C. inclusive. 
     
     
       16. A method according to claim 12, wherein step (b) is conducted by directing radiant heat from radiant heating means which includes a plurality of heaters disposed along said path. 
     
     
       17. A method according to claim 12, further comprising the step of controlling the intensity of the radiation directed toward said zone of impingement by adjusting the distance between said radiant heating means and said substrate. 
     
     
       18. A method according to claim 12, further comprising the step of controlling the intensity of the radiation directed toward said zone of impingement so that for any incremental area at the surface of the substrate which is being coated, the temperature varies by less than 15° C. between the time when said incremental area is first coincident with said zone of impingement and the time when said incremental area is last coincident. 
     
     
       19. A method according to claim 18, wherein the temperature varies by less than 10° C. between the time when said incremental area is first coincident with said zone of impingement and the time when said incremental area is last coincident. 
     
     
       20. A method according to claim 12, wherein step (b) is conducted by directing heat from radiant heating means which includes a plurality of heaters disposed across said path so that the quantities of heat directed toward different width increments of said substrate are independently adjustable. 
     
     
       21. A method according to claim 20, further comprising controlling the radiant heat so that, for any increment of the length of the substrate, the temperature of the surface being coated varies by less than 15° C. across the substrate width during coating. 
     
     
       22. A vitreous material coated by a method according to claim 12.